In accordance with a rapid spread of information relevant apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric automobile or a hybrid automobile has been advanced also in the industrial field such as the automobile industry. A lithium battery has been presently noticed from the viewpoint of a high energy density among various kinds of batteries.
Liquid electrolyte containing a flammable organic solvent is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, a lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte layer is conceived to intend the simplification of the safety device and be excellent in production cost and productivity for the reason that the flammable organic solvent is not used in the battery. In addition, a sulfide solid electrolyte material has been known as a solid electrolyte material used for such a solid electrolyte layer.
The sulfide solid electrolyte material is so high in Li ion conductivity as to be useful for intending higher output of a battery, and various kinds of research have been conventionally made. For example, in Patent Literature 1, Li2S—P2S5-based lithium ion conductor crystal glass and a battery using this as a solid electrolyte are disclosed. Also, in Non Patent Literature 1, a sulfide solid electrolyte material with a ratio of Li2S/P2S5=2, containing LiI, is disclosed. In addition, in Non Patent Literature 2, an LiI—Li2S—P2S5-based amorphous material obtained by a mechanical milling method is disclosed. Also, in Patent Literature 2, in order to restrain a reaction of a cathode active material and a solid electrolyte, a nonaqueous electrolyte battery selecting a combination of the solid electrolytes for a specific combination is disclosed.